[55.01] GSC-II: An Overview of the Database System

G. Greene, B. McLean (STScI), A. Volpicelli (OATo)

The Catalogs and Surveys Branch of the Space Telescope
Science Institute, in collaboration with a number of other
institutions, is constructing an all-sky catalog of
astronomical objects to support the operations of current
and future ground and space based telescopes. It is being
generated from the application of image processing and
object recognition techniques to digitized photographs taken
from the Palomar and UK Schmidt survey telescopes. To
accurately calibrate these data, it is crucial that we be
able to support cross-references between the internal
observations and to other external astronomical databases.
This database is expected to contain about 15 billion
measurements of 2 billion individual stars and galaxies, and
will be about 4TB in size.

For efficient access to objects, we have partitioned the sky
into 32768 equal-area spatial regions, each of which is the
leaf node of a Hierarchical Triangulated Mesh (HTM)
Quad-Tree and is an Objectivity Database. Individual plate
measurements and catalogues are stored as containers within
each database, along with a master index container which is
used to provide low-overhead links between object
measurements and external references.

We have currently constructed the individual databases for
our production system, and have already loaded the
measurements from the first Guide-Star Catalogue, which was
previously constructed to support the Hubble Space
Telescope. Additional measurements are now being loaded into
this federated database and we expect to complete catalogue
construction and calibration over the next 2-3 years.

We also give an overview of the planned capabilities of the
database to allow the exchange of information between this
and other external distributed databases such as the SDSS or
2MASS who plan on adopting the same sky partitioning scheme.
This will allow for efficient cross-identification of
objects from different databases and will provide a powerful
tool for future researchers.